Depth cues based on dynamic changes in the retinal projection supplement stereoscopic depth in normal vision, and may be especially important to persons lacking stereoscopic vision. The effectiveness of two dynamic monocular cues--velocity gradients and occlusion (the covering and uncovering of more distant objects by nearer objects)--will be studied for subjects with normal binocular vision and with dysfunctions in stereoscopic depth perception. A three part approach is proposed: (1) The first part addresses unresolved questions about the effectiveness of dynamic monocular cues for persons with normal stereoscopic vision. The first experiment contrasts the effectiveness of dynamic occlusion and perspective in providing relative distance information. The second experiment extends research on occlusion to scenes lacking distinct contours. The third experiment examines the trade--off between velocity, texture density, and observation time in determining the accuracy with which relative distance can be judged from a velocity gradient. (2) The second part addresses the question of whether the ability to perceive relative distance on the basis of dynamic monocular cues is affected by deficits in stereoscopic vision. Recent studies of dynamic cue effectiveness will be replicated with a clinical population. (3) The third part examines the use of monocular/stereoscopic conflict tests as measures of reliance on stereoscopic vision. These measures would supplement tests of stereoacuity. Subjects varying in stereoacuity will be asked to make relative depth judgments when velocity gradients or dynamic occlusion provide depth information opposite to that provided by stereoscopic cues. In addition to increasing understanding of dynamic monocular depth cues, this research should lead to improved methods for assessing the depth perception of persons lacking stereoscopic vision, methods for training such persons in the more effective use of monocular cues, and measures of the relative reliance on monocular as opposed to stereoscopic cues by persons during improvement or increased dysfunction in stereoacuity.